In many fabricating processes, plans are generated that estimate the quantity of a product that may be fabricated by a specific date. The plans are used by multiple organizations to plan and monitor the work flow in each respective area. For example, fabricating semiconductor chips generally involves fabricating wafers and performing tests on the wafers or individual die. A fabrication plan is created to estimate the fabrication schedule and quantities of semiconductor chips that may be fabricated within a given time frame or on a specific date.
The fabrication plan is utilized by a test organization to generate a testing plan. The testing plan generally takes as input the quantity of wafers expected to be fabricated on a specific date and determines the quantity of wafers that are to be tested on each day. As indicated above, the testing plan is very dependent upon the fabrication plan.
Many times, however, the plans are not accurate. Large variances between the planned and actual values may have a significant impact on successive systems and processes. For example, if the fabrication plan over estimates the quantity of wafers produced on a specific date, then the testing system may have idle equipment or workers that could be used for another task. Similarly, if the fabrication plan under estimates the quantity of wafers produced on a specific date, then the testing system may not have sufficient equipment and/or workers available to process the quantity provided by fabrication in a satisfactory time frame.
Therefore, there is a need for monitoring manufacturing systems to measure the accuracy of the fabrication plans such that the fabrication plans may be updated to produce more accurate plans.